Question: Simplify the following expression: $a = \dfrac{3p}{10} - \dfrac{4p}{5}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $10$ and $5$ $\lcm(10, 5) = 10$ $ a = \dfrac{1}{1} \cdot \dfrac{3p}{10} - \dfrac{2}{2} \cdot \dfrac{4p}{5} $ $a = \dfrac{3p}{10} - \dfrac{8p}{10}$ $a = \dfrac{3p -8p}{10}$ $a = \dfrac{-5p}{10}$ Simplify the expression by dividing the numerator and denominator by 5: $a = \dfrac{-p}{2}$